Answer:
Both genetic and environmental factors play a role in promoting various trait. The growth of a plant will first of all depend on the alleles which it carries. If the plant has alleles which promote plant growth then the plant will grow more than the plants not having those alleles.
Apart from the genes, the environment also has a role to play in the growth of a plant. The amount of sunlight, the nutrition, temperature, pH are all environmental factors which will either enhance the plant growth or will suppress it.